Lubricant distributors of the above-described type are as such adequately known. They serve to deliver the lubricant in a metered manner to the lubrication points. They are frequently embodied in block construction and are designed for delivery of various metering volumes, wherein each lubricant distributor can include on each of its two end sides, for example, two threaded bores for the selective connection of two main lines of a centralized lubrication system. The lubricant distributor has, for example, eight threaded bores for connecting the lines to the lubrication points. The lubricant metering itself is effected by a metering piston, which is movably disposed in the lubricant distributor housing in a cylinder bore. With each stroke of the metering piston a defined quantity of lubricant is delivered. A control piston is usually provided for the controlling of the metering piston. The control piston opens and closes the two main lines. Depending on the pressurization of the first or the second main line, the control piston moves in the one or the other direction and thus releases one of the two main lines, whereby the metering piston also subsequently moves and delivers a corresponding quantity of lubricant.
In addition to these 2-line distributors, the same also analogously applies, of course, in the case of other embodiments, for example in the case of a progressive distributor.
A lubricant distributor of the above-mentioned type is disclosed in US 2006/0243529 A1. Lubricant distributors of a similar type are known, for example, from U.S. Pat. No. 5,926,018 A, from US 2010/0282542 A1, from DE 10 2006 012 810 A1, and from DE 10 2006 001 317 A1. In these documents the general function of the distributor is described in detail and the functionality explained in detail. In this respect reference is expressly made to these documents.
In the literature mentioned the problem is also already recognized that it is useful, and can be necessary for proper operation, to monitor the movement of the metering piston, i.e. to determine whether the metering piston completely performs its intended metering stroke. However, the measures described here are in part technically complex and therefore expensive. In particular, it is difficult to monitor the lubricant lines after the lubricant distributor, and namely both as regards a possible blockage of a line and as regards the possible tearing of a line.